[Smart Lock] Add a private API to show an error bubble anchored to the Smart Lock app window.

chrome/common/extensions/api/easy_unlock_private.idl

Index: chrome/common/extensions/api/easy_unlock_private.idl
diff --git a/chrome/common/extensions/api/easy_unlock_private.idl b/chrome/common/extensions/api/easy_unlock_private.idl
index 4ab42327fa9f2608e76c72d59f0e1de0ea384072..656c9c4679ea0d01d731ddf1affc9ddbb052174a 100644
--- a/chrome/common/extensions/api/easy_unlock_private.idl
+++ b/chrome/common/extensions/api/easy_unlock_private.idl
@@ -148,6 +148,20 @@ namespace easyUnlockPrivate {
     boolean dataReady;
   };
 
+  // A range.
+  dictionary Range {
+    long start;
+    long end;
+  };
+
+  // A rectangle.
+  dictionary Rect {
+    long left;
+    long top;
+    long width;
+    long height;
+  };
+
   // Callback for crypto methods that return a single array buffer.
   callback DataCallback = void(optional ArrayBuffer data);
 
@@ -315,6 +329,15 @@ namespace easyUnlockPrivate {
 
     // Gets the user's profile image as a bitmap.
     static void getUserImage(DataCallback callback);
+
+    // Shows an error bubble with the given |message|, anchored to the given
+    // |anchorRect|. If the |link_range| is non-empty, renders the text within
+    // the |message| that is contained in the |link_range| as a link with the
+    // given |link_target| URL.
+    static void showErrorBubble(DOMString message,
+                                Range link_range,
+                                DOMString link_target,
+                                Rect anchorRect);
   };
 
   interface Events {